Platform over-clocking solutions provide performance enhancements for high end desktop and server processor products. Over-clocking is the process of making a computer or component operate faster than a clock frequency specified by the manufacturer by modifying system parameters. A key ingredient to over-clocking solutions is a low-jitter over-clockable base clock for the processor cores (e.g., in a multi-core processor) and memory controllers. For example, the frequency of a base clock is slowly increased from 100 MHz until the platform hits its thermal and operational limits. The platform is then rebooted at this elevated base clock frequency to achieve performance improvements.
Typically, this base clock is generated using an LC-oscillator based Phase Locked Loop (PLL), which then provides multiple high frequency clock phases for phase interpolator or delay locked chain circuits to realize the over-clocking feature. Such implementations consume large silicon footprint along with power penalty (i.e., leakage and active power) during non-over-clocking operation of platforms. Ring oscillator based PLLs are also used to generate over-clockable base clocks, but these implementations usually give very poor clock jitter performance.